The probe of a theft of nerve gas puts McGarrett on Wo Fat's (Khigh Dhiegh) trail, which leads to Hong Kong and a case of amnesia for himself.
Dina Merrill, David Tomlinson, Michael Anderson Jr. and Ric Young guest stars.
McGarrett fears a rapist-murderer (William C. Watson) roaming Oahu will find a girl (Laurie Prange) lost in the mountains before Five-O can rescue her.
An elderly man (Barnard Hughes) wires himself to a bomb and takes hostages to halt his home's demolition.
Mainland gangster needing a place to launder money tries to force a football-club owner to sell his team.